A pilotless aircraft is called “unmanned aerial vehicle”, and is an unmanned aircraft manipulated by using a radio remote control apparatus and a self-contained program control device. Amphibian unmanned aerial vehicles are usually mainly used in aerial flight, and can perform a short navigation in the water when executing a task over water areas such as a sea surface. However, the existing unmanned aerial vehicles can only be used as flight toys. They can neither navigate on water, nor achieve an amphibian function either. Therefore, the pleasure from using the existing unmanned aerial vehicles is limited.